PACAP-induced ectopic activity originating from the pulmonary vein was associated with large Ca(2+) transient amplitudes and was always suppressed by the Ca(2+) channel blocker verapamil (P<0.05).
Does PACAP-induced autonomic imbalance cause Ca(2+)-mediated triggered activity and pulmonary vein ectopy in canine left atrium preparations?
Autonomically mediated pulmonary vein ectopy may be driven by calcium-mediated triggered activity arising from delayed afterdepolarizations.
Tasa de eventos absoluta: 88.9% vs 0%
valor p: p=<0.05
Paroxysmal atrial fibrillation associated with focal ectopy originating from the pulmonary vein (PV) can be preceded by variations in autonomic tone; however, the underlying cellular mechanisms are not clear. To determine the mechanisms of autonomically mediated PV ectopy, high-resolution optical mapping techniques were used to measure action potentials and Ca(2+) transients from the PV and the ligament of Marshall area in the arterially perfused canine left atrium. Rapid pacing was used to initiate ectopic activity during pituitary adenylate cyclase-activating polypeptide (PACAP) injection (1 nmol), as a surrogate for autonomic imbalance, before (n = 9) and after (n = 6) verapamil (10 nmol) administration. In all preparations, spontaneous activity was absent before rapid pacing. During PACAP injection, rapid pacing induced ectopic activity in eight of nine preparations. In contrast, before PACAP injection, rapid pacing did not induce ectopic activity. Activation maps of each episode of ectopic activity indicated that the site of origin occurred more frequently in the PV (70%) than in the ligament of Marshall (30%) area. As rapid pacing cycle length increased, so did the ectopic beat coupling interval. In addition, PACAP-induced ectopic activity was associated with large Ca(2+) transient amplitudes and was always suppressed by verapamil, a Ca(2+) channel blocker (P < 0.05). Finally, during PACAP injection in the absence of an ectopic beat, spontaneous Ca(2+) release and delayed afterdepolarizations were observed simultaneously after termination of rapid pacing. In conclusion, these data suggest that autonomically mediated PV ectopy may be due to Ca(2+)-mediated triggered activity arising from delayed afterdepolarizations.
Hirose et al. (Sat,) conducted a other in Paroxysmal atrial fibrillation / pulmonary vein ectopy (n=9). PACAP injection and rapid pacing vs. Before PACAP injection was evaluated on Induction of ectopic activity (p=<0.05). PACAP-induced ectopic activity originating from the pulmonary vein was associated with large Ca(2+) transient amplitudes and was always suppressed by the Ca(2+) channel blocker verapamil (P<0.05).